At the end of the project, visitors to the National Trust run house and garden will once again be able to enjoy walking across the bridge.
It was designed by Lord Armstrong not only to provide easy access to the garden, but also to serve as a vantage point to survey the house, Debdon Valley, Tumbleton Lake and the Northumbrian hills beyond.
Cragside property manager, John O'Brien, said: "It is wonderful to begin the restoration of this magnificent iron bridge which is also a piece of sculpture in its own right.
"This is almost the final piece in the jigsaw of a £6 million investment in Cragside," he explained.
"It will allow visitors access from the rock garden to the formal garden and provide an excellent viewing platform for the house.
"The works are scheduled to be completed ready for the opening of the property next spring."
From 1863, William George Armstrong began purchasing the land at Cragside in parcels.
At this time, the house was modest in comparison to the great country house visitors can see today, but a series of extensions in 1870 saw the creation of an extraordinary Victorian house.
Not content with creating a wonderful house and landscape, Lord Armstrong also set about developing five lakes that would be used to provide hydro-electric power for the house.
The Grade II listed bridge has become an iconic structure within the landscape, but when the National Trust purchased the property in 1977, consulting engineers deemed it too hazardous to the public and gates were fitted at each end of the bridge to prevent public access.
The programme of works will ensure the historic significance and the aesthetic qualities of the bridge are preserved.
New decking, additional stantions either side of the walkway and steel mesh fitted to the sides will see the bridge returned to its former glory in time for visitors next year.
The conservation work to the bridge is being undertaken by Balfour Beatty.
To mark the occasion of the bridge's restoration, visitors to the formal gardens will be in for a treat as the head gardener and her team have created two carpet bed displays depicting the bridge and its restoration.
Alison Pringle, head gardener, said: "Carpet bedding was a Victorian approach to annual bedding using low-growing foliage plants.
"The idea was to produce a smooth, patterned surface inspired by Persian rugs and carpets, and was introduced to Cragside by Lord Armstrong, so it seemed very relevant to make this year's beds feature the iron bridge."
In total, almost 25,000 plants have been used for the two beds – the lower bed featuring a stylised image of the bridge and the top bed featuring a series of circles each depicting details from the original engineers drawings.
Alison continued: "It has been a real pleasure to re-introduce a popular feature to Cragside and we expect that the display will be looking its best from mid-August to October."
The project is being part financed by the European Union European Regional Development Fund, through the Northumberland Strategic Partnership.
Further information on the bridge restoration process will be displayed on property for visitors to find out more about work that is being undertaken.